Early agricultural planters for simultaneously planting plural spaced rows of crops using seed metering apparatus for dispensing seeds at a controlled rate provided each seed metering unit with its own seed hopper. The limited space available along the length of the planter's tool bar restricted the size of the individual row unit hoppers and led to the use of a central seed hopper for supplying plural smaller remote hoppers, or bins, each associated with a respective row unit. Plural hoses, or tubes, connect the central seed hopper to each remote bin of an individual seed metering unit. The seed bin of a seed metering device is typically integrated in the housing of the seed meter.
Air under pressure is used to move the seeds from the central seed hopper via the aforementioned tubes extending to the individual remote seed meters. Seeds in the main hopper are agitated by and entrained within an air stream and are delivered under pressure to the individual seed meters. In this type of distribution system, it is difficult to provide uniform seed agitation and transport via airstream entrainment to all individual remote seed meters to ensure uniform seed deposit in all of the crop rows. Inline air current which is too low will result in a reduced number of seeds being transported to the seed meters, while too high an air current may result in excess seed accumulation causing more than one seed to be discharged at a given time or interruptions in seed flow preventing deposit of seeds at regular intervals. Attempts to address this problem have led to the introduction of large remote hoppers having sufficient seed capacity to compensate for any reduction or interruption in the flow of seeds to any of the remote seed meters. But this approach has met with only limited success because of the limited space on the toolbar and the close spacings of the crop rows as discussed above.
The present invention addresses the aforementioned limitations of the prior art by providing a means of variable air dissipation in a compressed air system for distributing seeds from one or more central hoppers to plural remote seed meters for timed deposit of individual seeds in the soil.